I. Field of the Invention
The present invention relates generally to auxiliary or tag load supporting axles for wheeled vehicles of the utility, load-hauling type which can be selectively deployed into ground-engaging, load supporting disposition or retracted to an elevated or stowed position. The present invention is more specifically directed to an improved mounting and pivoting system for such auxiliary axle systems which is particularly adapted to be attached to the rear of a transit concrete mixing truck.
II. Related Art
Transit concrete mixing trucks typically include a cab for the operator and a rotatable drum behind the cab for containing and mixing of concrete ingredients. Such trucks further typically include a single set of forward steering wheels and a plurality of rear, load supporting drive axles carrying dual wheel arrangements all mounted on an elongated continuous chassis. For additional support, particularly in transit when the drum is substantially full, a mixing truck can benefit by having a pivotally mounted auxiliary axle able to operate between a raised position wherein it is carried by the truck and a lowered or deployed position wherein the auxiliary axle and its wheels share the truck's load with the permanent steering and drive wheel system.
Not only does the auxiliary or tag axle system assist in balancing the load carried by the transit cement truck when the drum is fully loaded, it may enable the cement truck to carry a higher total payload than would otherwise be permitted. This is because weight restrictions placed on vehicles traveling over highways by states and/or the federal government to prevent undue deterioration of highways and road surfaces are typically measured in terms of load per axle in combination with overall spacing between axles of a vehicle. By deploying an auxiliary or tag axle system, the number of axles as well as the spacing thereof can be temporarily increased when the truck is heavily loaded thereby enabling it to transport a higher total legal payload.
The related art is replete with numerous devices designed to achieve the foregoing end. Examples of such systems, particularly with regard to transit cement mixer vehicles, include U.S. Pat. No. 4,684,142 to Ronald E. Christenson, the inventor herein, and assigned to the same assignee as the present invention. That patent relates to a tag axle assembly and means for mounting it to a transit concrete mixing truck. The system is operable by a pair of pneumatic load springs extensible to pivot the assembly downward to operating position and a pair of pneumatic lift springs extensible to pivot the assembly upward to the raised or stowed position. The assembly includes a tag axle frame having a forward longitudinally extending stem and two rearward extending and diverging legs. The '142 system is particularly directed to improved tracking during turns and enabling adjustment to uneven terrain.
Another tag axle assembly for a work vehicle, particularly a transit cement mixing vehicle, is described in U.S. Pat. No. 4,848,783 to Ronald E. Christenson (the inventor herein) et al and assigned to the same assignee as the present invention. That invention is particularly concerned with a multi-hydraulic cylinder arrangement that enables the wheels to be raised a significantly greater distance above the ground than was previously the case. The '783 patent shows a cantilevered mounting system in FIG. 9. Because the pin is cantilever mounted, however, there is nothing to further stabilize the pin and it tends to wobble and cause undue wear of the mounting joint.
As illustrated by Brennan et al in U.S. Pat. No. 3,191,961, it is also known to mount bearing housings atop the chassis structural members or beneath the chassis structural members as shown generally in U.S. Pat. No. 3,112,100 to Prichard. These are mounted from the rear of transit concrete mixing vehicles. The spaced tag axle arms are carried by shafts or pivot pins journalled in these bearings.
Earlier devices have been satisfactory in many respects; however, one of the chronic shortcomings of many is related to the connection between the tag axle assembly and the rear of the vehicle. Many previous arrangements have experienced undue wear in connection with the pivoting points on which the tag axle assembly is mounted and about which it pivots for stowage and deployment.
It is therefore a principal object of the present invention to provide an improved articulating tag axle mounting assembly for a work vehicle.
Another object of the invention is to reduce wear in a tag axle assembly mounting system.
A further object of the invention is to provide a novel tag axle mounting assembly in which spaced sides of the assembly are pivoted each using a dual spherical bearing arrangement.
Still another object of the invention is to provide a novel tag axle mounting assembly in which the sides of the assembly are pivotally mounted each utilizing single spherical bearing arrangement in the mounting of the auxiliary axle to the truck frame.
Yet still another object of the invention is to provide a novel pivotal mounting assembly for a tag axle system wherein the tag axle system is pivotally mounted utilizing a pair of spaced elastomer filled journal bearing arrangements, one associated with each side of the system.
Still a further object of the invention is to provide a rugged, long-lasting deployable tag axle mounting assembly for a tag axle associated with a work vehicle such as a ready-mix concrete truck which either when stowed or fully extended is completely independent of and does not interfere with the chute used in unloading the vehicle.
A yet still further object of the invention is to provide an improved mounting assembly for a tag axle system for a transit concrete mixing vehicle that uses a stabilized bearing mount but does not diminish the interaxle distance.
These and other object and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a plurality of embodiments, especially when considered in conjunction with the accompanying claims and drawings.